Insights about the epidemiology of Salmonella Typhimurium isolates from different sources in Brazil using comparative genomics.

BACKGROUND: Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) is an important zoonotic agent worldwide. The aim of this work was to compare genetically 117 S. Typhimurium isolated from different sources over 30 years in Brazil using different genomics strategies. RESULTS: The majority of the 117 S. Typhimurium strains studied were grouped into a single cluster (≅ 90%) by the core genome multilocus sequence typing and (≅ 77%) by single copy marker genes. The phylogenetic analysis based on single nucleotide polymorphism (SNP) grouped most strains from humans into a single cluster (≅ 93%), while the strains isolated from food and swine were alocated into three clusters. The different orthologous protein clusters found for some S. Typhimurium isolated from humans and food are involved in metabolic and regulatory processes. For 26 isolates from swine the sequence types (ST) 19 and ST1921 were the most prevalent ones, and the ST14, ST64, ST516 and ST639 were also detected. Previous results typed the 91 S. Typhimurium isolates from humans and foods as ST19, ST313, ST1921, ST3343 and ST1649. The main prophages detected were: Gifsy-2 in 79 (67.5%) and Gifsy-1 in 63 (54%) strains. All of the S. Typhimurium isolates contained the acrA, acrB, macA, macB, mdtK, emrA, emrB, emrR and tolC efflux pump genes. CONCLUSIONS: The phylogenetic trees grouped the majority of the S. Typhimurium isolates from humans into a single cluster suggesting that there is one prevalent subtype in Brazil. Regarding strains isolated from food and swine, the SNPs' results suggested the circulation of more than one subtype over 30 years in this country. The orthologous protein clusters analysis revealed unique genes in the strains studied mainly related to bacterial metabolism. S. Typhimurium strains from swine showed greater diversity of STs and prophages in comparison to strains isolated from humans and foods. The pathogenic potential of S. Typhimurium strains was corroborated by the presence of exclusive prophages of this serovar involved in its virulence. The high number of resistance genes related to efflux pumps is worrying and may lead to therapeutic failures when clinical treatment is needed.

Correction: Phenotypic and genotypic characterization of Salmonella Typhimurium isolates from humans and foods in Brazil.

[This corrects the article DOI: 10.1371/journal.pone.0237886.].

Phenotypic and genotypic characterization of Salmonella Typhimurium isolates from humans and foods in Brazil.

Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) causes gastroenteritis in many countries. However, in Brazil there are few studies that have conducted a virulence characterization of this serovar. The aim of this study was to evaluate the virulence potential of S. Typhimurium strains isolated in Brazil. Forty S. Typhimurium strains isolated from humans (n = 20) and food (n = 20) from Brazil were studied regarding their invasion and survival in human epithelial cells (Caco-2) and macrophages (U937). Their virulence potential was determined using the Galleria mellonella larvae model combined with the analysis of virulence genes by whole genome sequencing (WGS). A total of 67.5% of the S. Typhimurium studied (32.5% isolated from humans and 35% isolated from food) invaded Caco-2 epithelial cells at levels similar to or greater than the S. Typhimurium SL1344 prototype strain. In addition, 37.5% of the studied strains (25% isolated from humans and 12.5% isolated from food) survived in U937 human macrophages at levels similar to or greater than SL1344. S. Typhimurium strains isolated from humans (40%) and food (25%) showed high or intermediate virulence in G. mellonella larvae after seven days exposure. Approximately, 153 virulence genes of chromosomal and plasmidial origin were detected in the strains studied. In conclusion, the ability of the S. Typhimurium to invade Caco-2 epithelial cells was strain dependent and was not related to the source or the year of isolation. However, S. Typhimurium strains isolated from humans showed greater survival rates in U937 human macrophages, and presented higher proportion of isolates with a virulent profile in G. mellonella in comparison to strains isolated from food suggesting that this difference may be related to the higher frequency of human isolates which contained plasmid genes, such as spvABCDR operon, pefABCD operon, rck and mig-5.

Incidência de aflatoxinas B1, B2, G1 e G2 em amendoins / Incidence of aflatoxins B1, B2, G1 and G2 in peanuts

Micotoxinas são substâncias tóxicas produzidas por fungos e encontradas nos alimentos. As micotoxinas mais tóxicas são as aflatoxinas, produzidas, principalmente por Aspergillus flavus. Estudos realizados no país demonstraram alta incidência dessas micotoxinas em produtos de amendoim, que representa risco à saúde da população. O objetivo do estudo foi avaliar a incidência de aflatoxinas B1, B2, G1 e G2 em amostras de amendoins comercializados na região Nordeste do Estado de São Paulo nos períodos de 1994-2001 e 2016-2017. O método utilizado para analisar as amostras no primeiro período foi extração líquido-líquido e cromatografia em camada delgada e no segundo foi utilizando colunas de imunoafinidade, cromatografia líquida com derivatização pós- coluna e detector por fluorescência. No levantamento de 1994-2001 das 82 amostras, 39% tiveram contaminação de aflatoxinas variando de 11 a 1556 µg/kg com 37% das amostras contendo níveis maiores que 20 µg/kg, enquanto na pesquisa de 2016-17, das 56 amostras, 38% apresentaram contaminação destas toxinas variando de 0,09 a 60,40 µg/kg com 13% das amostras contendo níveis maiores que 20 µg/kg. Os resultados dos dois períodos estudados indicam que houve uma diminuição na incidência e nível das aflatoxinas estudadas, embora esta contaminação em amendoim permaneça um problema de saúde pública. (AU)

Mycotoxins are toxic compounds produced by fungi found in food. The most toxic mycotoxins are the aflatoxins produced mainly by Aspergillus flavus . Studies carried out in Brazil showed a high incidence of these mycotoxins in peanut products, a fact that represents public health problems. The aim of the study was to evaluate aflatoxins B1, B2, G1, and G2 in samples of peanuts sold in cities of the Northeast of the State of São Paulo in the period from 1994 to 2001 and from 2016 to 2017. The samples of the first period were analyzed using liquid-liquid extraction and thin-layer chromatography and the second using immunoaffinity columns, post-column derivative liquid chromatography and fluorescence detector. In the 1994-2001 survey, among 82 samples, 39% presented aflatoxins contamination ranging from 11 to 1556 µg/kg with 37% with levels greater than 20 µg/kg whereas, in the 2016-17 survey, 38% of the 56 samples presented contamination of aflatoxins ranging from 0.09 to 60.40 µg/kg and 7 samples 13% containing aflatoxins levels higher than 20 µg/kg. The results indicated there was a decrease in the incidence and level of aflatoxins, but the contamination of aflatoxins in peanuts remains a public health problem. (AU)

Incidência de aflatoxinas B1, B2, G1 e G2 em amendoins / Incidence of aflatoxins B1, B2, G1 and G2 in peanuts

Micotoxinas são substâncias tóxicas produzidas por fungos e encontradas nos alimentos. As micotoxinas mais tóxicas são as aflatoxinas, produzidas, principalmente por Aspergillus flavus. Estudos realizados no país demonstraram alta incidência dessas micotoxinas em produtos de amendoim, que representa risco à saúde da população. O objetivo do estudo foi avaliar a incidência de aflatoxinas B1, B2, G1 e G2 em amostras de amendoins comercializados na região Nordeste do Estado de São Paulo nos períodos de 1994-2001 e 2016-2017. O método utilizado para analisar as amostras no primeiro período foi extração líquido-líquido e cromatografia em camada delgada e no segundo foi utilizando colunas de imunoafinidade, cromatografia líquida com derivatização pós-coluna e detector por fluorescência. No levantamento de 1994-2001 das 82 amostras, 39% tiveram contaminação de aflatoxinas variando de 11 a 1556 μg/kg com 37% das amostras contendo níveis maiores que 20 μg/kg, enquanto na pesquisa de 2016-17, das 56 amostras, 38% apresentaram contaminação destas toxinas variando de 0,09 a 60,40 μg/kg com 13% das amostras contendo níveis maiores que 20 μg/kg. Os resultados dos dois períodos estudados indicam que houve uma diminuição na incidência e nível das aflatoxinas estudadas, embora esta contaminação em amendoim permaneça um problema de saúde pública.

Mycotoxins are toxic compounds produced by fungi found in food. The most toxic mycotoxins are the aflatoxins produced mainly by Aspergillus flavus. Studies carried out in Brazil showed a high incidence of these mycotoxins in peanut products, a fact that represents public health problems. The aim of the study was to evaluate aflatoxins B1, B2, G1, and G2 in samples of peanuts sold in cities of the Northeast of the State of São Paulo in the period from 1994 to 2001 and from 2016 to 2017. The samples of the first period were analyzed using liquid-liquid extraction and thin-layer chromatography and the second using immunoaffinity columns, post-column derivative liquid chromatography and fluorescence detector. In the 1994-2001 survey, among 82 samples, 39% presented aflatoxins contamination ranging from 11 to 1556 μg/kg with 37% with levels greater than 20 μg/kg whereas, in the 2016-17 survey, 38% of the 56 samples presented contamination of aflatoxins ranging from 0.09 to 60.40 μg/kg and 7 samples 13% containing aflatoxins levels higher than 20 μg/kg. The results indicated there was a decrease in the incidence and level of aflatoxins, but the contamination of aflatoxins in peanuts remains a public health problem.